Exercise device



FIG. 1 is a front view of the new design;

FIG. 2 is a top view of the new design; and,

FIG. 3 is an enlarged left side perspective view of the new design.

The broken line showing of FIGS. 1-3 are for illustrative purposes only and forms no part of the claimed design.

The back view is identical to the front view. The bottom view is identical to the top view. The right side perspective view is identical to the left side perspective view. 

The ornamental design for an exercise device, as shown and described. 